Thistle

Circium sp.

Thistle. Is it a beautiful purple wildflower that generously produces nectar for butterflies and seeds for small birds like the American Goldfinch? Or, is it a treacherous weed of fields and pastures that is a scourge for farmers everywhere? Can I paint a fair portrait?

It is both. This prickly plant bears plump flower heads on tall stems, in various shades of pink, lilac, and purple. Pollinators flock to the nectar-rich blooms, and a field of thistle may be one of the best places I can think of to find an assortment of bees and butterflies at work. After thistle flowers whither, the ovary swells and produces a mass of silky, feathery seeds that are carried away by the wind. This pink pincushion of a flower is morphologically fascinating at each stage of its development, and therefore I will argue, it is lovely in its own way.

This may be the world’s tallest bull thistle: 10 feet, 7 inches tall!

However, thistles have developed an elaborate defense system to prevent mammals from grazing on them. Practically every part of the plant is sharp and prickly. Ouch, don’t bump into one! This inconvenient feature of the plant makes it very hard to manage, especially if you have a lot of it on your property. For farmers, thistles are simply noxious weeds that deserve eradication.

There are many species of thistles, including the locally common Bull thistle, Canada thistle, Plumeless thistle, Nodding or Musk thistle, and Field thistle. Some are native and some are introduced. You can find thistles blooming throughout the summer and they are are never hard to find! Ask any butterfly!

Click on any image for a larger view:

Thistle

Thistle leaf

leaves 4-8 inches, deeply pinnate and spiny

Stem hairy

American Goldfinch eating thistle seeds. Photo by Will Sweet (Wikipedia)